The present invention relates to television video processing, and more particularly to a means for displaying a television picture simultaneously with a measurement display on a television test and measurement instrument.
A television test and measurement instrument displays in analog form selected video lines of data from a television video signal, either as a signal waveform or as a chrominance vector display. Essentially the measurement instrument is a special purpose oscilloscope which automatically triggers on a horizontal sync pulse from the input video signal and has internal circuitry for detecting and selecting a specific field and horizontal line of video information for processing and display. In order to see the effect on a television picture of an anomaly noted on a measurement instrument, a separate picture monitor is required. When observing video signals within a control room or studio environment, there is usually a monitor readily available. However in the field it is often desirable to observe both the measurement display and the effect on a television picture simultaneously. Currently this requires both the television monitor and the measurement instrument, which adds to the amount of equipment required by a service technician.
A prior instrument, the 2710 Spectrum Analyzer manufactured by Tektronix, Inc. of Beaverton, Oreg., has a video monitor option that allows a video signal to be displayed on the same screen as that used to display the spectrum of an input signal. For a video display the video input signal is switched to be input to the Z-axis driver of the display cathode ray tube (CRT), and also is switched to be input to a sync generator circuit to extract horizontal and vertical sync signals that are used to generate horizontal and vertical ramp signals at television rates to provide a raster display on the monitor of the input video signal.
Another prior instrument, the 1720 Vectorscope also manufactured by Tektronix, Inc. of Beaverton, Oreg., has a simultaneous display feature that is described in co-pending U.S. patent application Ser. No. 07/274,689, a continuation of an application filed originally on Mar. 17, 1986. This feature allows two signals that require different processing techniques, such as chrominance vector signals from chrominance demodulators and stereo audio signals from audio amplifiers, to be displayed apparently simultaneously on the same monitor by switching between the two Signal sources at a rate that is unrelated to the horizontal line rate to prevent beat frequencies.
What is desired is a test and measurement instrument that combines the features of a test and measurement instrument and a picture monitor into a single instrument to display simultaneously a video picture and a measurement display for an input video signal.